Lattice structure and microwave dielectric properties of [Mg0.5Si0.5]3+-doped LiAlO2 solid solution
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Microwave dielectric properties of low-permittivity LiAl1−x(Mg0.5Si0.5)xO2 (LAMS) (x = 0.02–0.2) ceramics synthesised through solid-state reaction route were investigated. All compositions show pure LiAlO2 phase with a P41212 space group at x ≤ 0.18. Microstructure and relative permittivity (εr) were greatly affected by the partial substitution of [Mg0.5Si0.5]3+ for Al3+ site. Bond energy decreased with increasing x value, thereby increasing the temperature coefficient of resonant frequency (τf) in the negative direction. Finally, the optimum microwave dielectric properties of LAMS (x = 0.02) sample were obtained at 1300 °C with εr = 6.17, Q × f = 53,300 GHz and τf = − 129 ppm/°C. Then CaTiO3 was added to the LAMS (x = 0.02) material to adjust the τf value to near zero.
This work was supported by the National Natural Science Foundation of China (NSFC-51572093 and 51772107), the Major Technological Innovation Projects in Hubei Province (2018AAA039), and the Research Projects Supported by the Equipment Development Department (1807WM0004). The authors are grateful to the Analytical and Testing Center, Huazhong University of Science and Technology, for SEM analyses.
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